Thermostatic electric heating appliance



Patented July. 6; 1937 UNITED sTATEs PATENT {OFFICE I aoaam mamos'ra'nc amc'rarc HEATING 4. arrmsx Application rennin-y 11, .1935, Serial No. 5,980

' '13 Claims. (01. 219-35) This invention relates to, automatic temperature-controlled electrically-heated appliances, and more particularly to an automatic flat-iron in which the on and of! switch for the heating element is directly operated by the expansion and contraction of the sole plate.

. One object of this invention is to provide a iiat-iron oi the above nature in which the temperature is maintained within very close limits, thus permitting a reduction of power input over that commonly used.

A further object is to provide a fiat-iron of the above nature in which the switch for opening and closing the circuit through the heating element is actuated by the toggle action of a pair of cooperating bars, the ends of which are seated upon a pair of spaced thrust members fastened to the sole'plate.

A further object is to provide a device of the above nature which will be simple in construction, inexpensive to manufacture, easy to assemble and manipulate, compact, ornamental in appearance, and very eiiicient and durable in use.

With these and other objects in view,' there has been illustrated on the accompanying drawing, one form in which the invention may be conveniently embodied in practice.

In the drawing: a g

Fig. 1 represents a longitudinal sectional view through a flat-iron embodying theinvention.

Fig. 2 is a plan view of the same with the top shell and associated parts removed,

Fig. 3 is a diagrammatic view of the thermostatic controlling mechanism, andthe electrical circuit automatically-controlled thereby.

Many attempts have been made in the past to provide an electric heatin g'appliance, such as a flat-iron, which would remain at a constant even to temperature, even 'whenthe heat demanded therefrom was variable In most irons it was necessary to employ'a heating elementI having a capacity exceeding the maximum heat consumption of the iron in order to shorten the delay or lag in the actionaoi the thermostat which was generally of the bimetallic strip type. Quch flatirons are relatively sluggish in action due to the relatively large temperature drop between the sole plate and the bimetallic unit or other heat controlling member.- This temperature drop is due to the fact-that the thermostat receives its heat indirectly by conduction, radiation or convection iromthe sole plate; and in fact, the

thermostat was sometimes insulated from the 56 soleplatebymicaorother'materials. flhe lagin such irons was still further increased by reason of the fact that the metals employed in the bimetallic strips were of relatively low heat con-v ductivity, and hence, were slow to respond to temperature changes. I 5

By means of the present invention, the above and other disadvantages have been avoided by so constructing the iron that the sole plate or other heat-applying element forms a part of the thermostatic mechanism. 10

Referring now to the drawing in which like ref erence numerals, denote corresponding parts throughout the several views, the numeral ill indicates a metal sole plate, preferably constructed of relatively thin metal so as to allow the heatl5 ing element to be positioned close to the, material being ironed, and to permit .the thermostatic control device to expand and contract more rapidly due to temperature changes. The sole plate i0 is located under a filler block ll of relatively thick metal,- and is secured thereto by a pair of upstanding bolts l2 and I3 having frusto-conical heads which, as shown in Fig. l, are adapted to be secured in a pair of circular recesses it provided in the upper surface of the sole plate ill. The bolts l2 and i3 extend upwardly through an elongated slot IS in the filler block I i.

The forward bolt I2 is tightly clamped upon' the filler block II by means of a nut It engaging the base section of an angle bracket 2| seated in -a depression it formed on the top of said filler block. The rear end of the flllerblock H is adapted to support a base plate It forming an integral part of a U-shaped prong-carrying shell Ill. The base plate 19 overlaps the rear end oi the longitudinal slot l5, and is tightly held down upon the iiller block II by means of a binding nut 22 screwed on the bolt 13.

A flat mica-enclosed heating element 23 oi the conventional U-shaped form is located in direct contact with the upper surface or the sole plate It, said heating element being separated from v the superimposed filler block H by a sheet'o'f asbestos material 24 having the same shape as said heating element 23. The terminals of the 45 heating element 23 are connected in an electric circuit, including a pair oi upstanding rearwardly inclined prongs 25 and a temperature responsive switch to be described later. The prongs 25 are i dly'connected to the U- haped shell 20;--be- 5 ing insulated theretrom'in the usual manner.

The upper part of the sole plate It and'asso- I ciated parts carried thereby are completely en- 7 closed by means of the usual thin metal cover shell 2. Provision is also madeoi a U-shaped handle bracket 27! having. its lower front end rigidly supported upon the cover shell 26. The bracket 2? supports a heat insulating tubular handle 28 held in place by means of an elongated bolt and nut, not shown, attached to the upper end of said bracket. The handle bracket 21 has a rearwardly-opening oval-shaped socket 29 surrounding the contact prongs 25. The cover shell 26 and its attached handle bracket 2'! is held in position on the top surface of the sole plate It! by means of a socket nut 30 screwed upon the upper end of the rear bolt l3.

Thermostatic mechanism The temperature-responsive switch operating mechanism includes three members:

A. The portion of the sole plate l0 lying between the bolts l2 and I3, said portion being conveniently indicated by the letter P;

B. A slightly inclined longitudinal thrust bar 3| provided with, oppositely beveled extremities 32 and 33,-the left-hand extremity 32, as shown in Fig. 3, being adapted to pivotally engage in a V-shaped notch 34 provided on'the rear side oil A the head of the bolt 2 and C. An inclined third class lever 36 having a reentrant angle bend 35 formed in the intermediate section thereof for receiving the righthand beveled extremity 33.

The lever 36 has a short lower end 37 provided with a beveled extremity 38 which is fulcrumed in a notch 39 in the head of the bolt I 3. From this construction it will be noted that the thrust bar 3| and the short end 31 of the lever 36 deflne the two short sides of a triangle in which the plate P constitutes the hypotenuse. p

The thrust bar 3| and the lever 36 are preferably constructed of a metal or metals having a. coefllcient of expansion considerably lower than the material of the sole plate l0. Consequently, when the plate "P" expands due to heat applied thereto from the heating element 23, the bar 3| and the cooperating lever 36 will swing downwardly under the influence of a downwardly pressing leaf-spring 40 having its opposite end rigidly anchored to the bolt l3 between a pair of opposed nuts 4|. The upper portion 42 of the lever 36 extends a considerable distance beyond the bend 35 thereoi', so that the expansion of the sole plate section P will be greatly magnified thereby. The portion 42 is bent at a slight angle and is normally in a substantially horizontal position and out of engagement with a thrust button 43 made 01 insulating material and carried on the lower leg 44 of a J-shaped movable contact bar 44a. The upper leg 44b of the contact bar 44a is considerably longer than the lower leg 44 thereof, and is secured, as by riveting, to the free end of a flat elongated leaf-spring 440. The other end of the leaf-spring 440 is made rigid to an angle support 45 which is electrically connected with the heating element 2 3. The upper leg 44b of the contact bar 44a carries a movable contact button 46, preterably of silver, adapted to normally engage *with a similar-contact button 41 riveted or otherwise secured to the free end or an adjustable resilient conductorstrip 43. The rear end 43a of the conductor strip 43 is bent laterally and is anchored toone oi. the contactor prongs 25, as by means of nuts 43. 1

In order tosimultaneously and manually ad- Just the vertical position of the upper button 41 access-o thrust spool 50 .of porcelain or analogous insulating material, which is adapted to freely pass through alined slots provided in the conductor strip 48 and the upper leg 44b of the J-shaped contact bar 44a, respectively. The upper end of the thrust spool 50 is provided with an enlarged head 5| which is adapted to engage the top surface of the conductor strip 48. An adjusting screw 52 is located in axialalinement with the bushing 50 and engages the top of the enlarged head 5|. The adjusting screw 52 is screwed into the upper horizontal section of the angle bracket 2| and has at its upper end a reduced section 52a which is adapted to pass through a tubular eyelet 53 located in the cover shell 26 and handle bracket 21. A manuallyoperated temperature-regulating arm 54 is secured to the top of said reduced section 5201.

Operation wardly, and alter a predetermined temperature is reached, causing the arm 42 to engage the insulating button 43 and causethe J-shaped bar 44a to separate the contact buttons 46 and 41 and open the circuit. When the plate'cools, the bar 3| and lever 36 will be caused to swing upwardly by a toggle action, causing the circuit to be again closed. The operating temperature of the fiat-iron may be readily fixed by manually rotating the screw 52 to the desired point, thereby varying the distance between the buttons 46 and 41.

While the thrust bar 3| and lever 36 have been herein described as made 01' metal, it will be understood that either or both of these parts may be made of any suitable material, such as quartz, quartz glass, carbon, or lava within the spirit andscope of this invention.

While there has been disclosed in this specification one form in which the invention may be embodied, it is to be understood that this form is shown for the purpose of illustration only, and that the invention is not to be limited to the specific disclosure but may be modified and embodied in various other forms without departing from its spirit. In short, the invention includes all the modifications and embodiments coming within the scope of the following claims.

Havingthus fully described the invention, what is claimed as new, and for which it is desired to secure Letters Patent, is:

1. In an electrically heated flat-iron, a sole plate, a heating element for supplying heat to said sole plate, a. circuit including a switch for supplying current to said element, a pair of oppositely inclined bars havingtheir lower ends in the other bar, said bars having a coeflicient of -ex-' pansion diflerent from that of said sole plate whereby said bars will be lowered and raised with respect to said plate coincident with the expansion and contraction thereof, and means responsive to the movement oi said bars for opening and closing said switch.

2. In an electrically heated flat-iron, a sole plate, a heating element for supplying heat to said sole plate, a circuit including a switch for supplying current to said element, a'pair of oppositely inclined bars having their lower ends in pivotal engagement with spaced points on said base, the upper endof one of said bars engaging an intermediate section of the other bar, said bars having a coeilicient of expansion difierent irom that ofi said sole plate whereby said bars will be lowered and raised with respect to said plate coincident with the expansion and contraction thereof, and means responsive to the movement of said bars for opening and closing said switch.

3. In an electrically heated flat-iron, a sole plate, a heating element for supplying heat to said sole plate, a circuit including a switch for supplying current to said element, a pair of oppositely inclined bars having their lower ends in pivotal engagement with spaced points on said plate, the upper end of one of said bars engaging the other bar, said bars having a coeflicient of expansion different from that of said sole plate whereby said bars will be lowered and raised with respect to' said plate coincident with the expansion and contraction thereof, and means responsive to the movement of said upper bar for opening and closing said switch.

4. In an automatic electric heating appliance, a heat applying member, an electric heating element for supplying heat to said member, a circuit including a switch and said heating element, an inclined bar and an oppositely inclined lever engaging said member at spaced points, said bar being fulcrumed between the ends of said lever forming a toggle, said bar and lever being constructed of a material having a lower coeiiicient of expansion than that of said heat applying member, and means responsive to the movement of the upper end of said lever for opening and closing said circuit.

5. In an automatic electric heating appliance,

a heat applying member, an electric heating element for supplying heat to said member, a circuit including a switch and said heating element, an inclined bar and an oppositely inclined spring-pressed lever engaging said member at spaced points, said bar being fulcrumed between the ends of said lever forming a toggle, said bar and lever being constructed of a material having a lower coelficient of expansion than that of said heat applying member, and means responsive to the movement of the upper end of said lever for opening and closing said circuit.

6. In an automatic electric heating appliance, a heat applying member, an electric heating element for supplying heat to said member, a circuit including a switch and-said heating element, an inclined bar and an oppositely inclined lever having an intermediate shoulder engaging said member at spaced points, said bar being fulcrumed in said shoulder forming a toggle, said bar and lever being constructed of a material having a lower coeifi cient of expansion than that of said heat applying member, and means responsive to the movement of the upper end of said lever for opening and closing said circuit.

7. In an automatic electric heating appliance, a wall member which is free to expand and contract, an electric heating element, a circuit including a switch and said heating element and having connections to a source of current, an inclined bar and an oppositely inclined lever engaging said wall member at spaced points, the other end of said bar being fulcrumed between the ends of said lever, said bar and lever being constructed of a material having a lower coefficient. of expansion than that of said wall member, and means responsive-to the movement of the 'free end of said lever for opening and closing said circuit.

8. In an automatic electric heating appliance, a wall member which is free to expand and contract, an electric heating element, a circuit includinga switch and said heating element and having connections to a source of current, an inclined bar and an oppositely inclined lever engaging said wall member at spaced points, the other end of said bar being fulcrumed between the ends of said lever, said bar and lever being constructed of a material having a lower coeflicient of expansion than that of said wall member, and a switch responsive to the movement of the free end of said lever for opening and closing said circuit.

9. In an electrically heated appliance, a heating plate, electrical means for heating said plate, an electric circuit for supplying current to said means, a switch for controlling said circuit, a pair of cooperating upwardly-extending s'vitchactuating toggle bars having their lower ends engaging a pair of spaced points on said plate, one or both of said toggle bars having a coefilcient of expansion different from that of said plate, the unequal expansion and contraction of said plate and bars causing said toggle bars to open and close said switch.

10. In an electrically heated flat-iron, a sole plate, an electrical heating element for supplying heat to said sole plate, a switch located above said sole plate for controlling a circuit for supplying current to said element, a pair of spaced notched heads embedded in the upper surface of said sole plate, a pair of upwardly-extending oppositelyinclined switch-actuating bars having their lower ends seated in pivotal engagement with the notches of said heads, one of said bars engaging the other bar and having a coefiicient of expansion different from that of said sole plate whereby said bars will be moved with respect to said plate by the expansion and contraction thereof, and means responsive to the movement of said bars for opening and closing said switch.

11. In an electrically heated fiat-iron, a sole plate, a heating element for supplying heat to said sole plate, a switch having a vertically movable contact located above said sole plate for controlling the supply of current to said element, a pair of oppositely inclined switch-actuating upstanding bars beneath said switch and having their lower ends in pivotal engagement with spaced points on said plate, the upper end of one of said bars engaging an intermediate section of the other bar, said first mentioned bar having a coefficient of expansion different from that of said sole plate whereby said bars will be lowered and raised with respect to said plate coincident with the expansion and contraction thereof, the up and down movement of said bars causing the opening and closing of said switch.

12. In an automatic electric heating appliance, a Wall member which is free to expand and contract, an electric heating element,a switchfor controlling a circuit including said heating element and having connections to a source of current, an upwardly extending inclined bar and an oppositely inclined switch-actuating lever engaging said wall member at spaced points, the upper end of said bar being fulcrumed between the ends of said lever, said bar being constructed of a material having a lower coefllcient oi. expansion than that of said wall member, the movement of the free end of said lever serving to open and close said switch.

13. In an automatic electric heating appliance,

' a wall member which is free to expand and contract,. an electric heating element therefor, a circuit including a switch and said heating element and having connections to a source of cur- 10 rent, an inclined bar and an oppositely inclined 

